Rubbing device

ABSTRACT

The present invention provides a rubbing device including a base roller assembly that suspends and otherwise supports a base film to convey the same in one direction; a rubbing roller assembly that suspends and otherwise supports a rubbing cloth, and that moves the rubbing cloth in a direction opposite a conveying direction of the base film to thereby realize a rubbing treatment by contact between the rubbing cloth and the base film; and a rotating apparatus provided under the rubbing roller assembly and that rotates the entire rubbing roller assembly to a particular angle within the range of 0-180° in the clockwise or counterclockwise direction with respect to the conveying direction of the base film.

BACKGROUND OF THE INVENTION

[0001] (a) Field of the Invention

[0002] The present invention relates to a rubbing device used in themanufacture of an optical compensation film. More particularly, thepresent invention relates to a rubbing device that allows for thesetting of a rubbing angle with respect to a moving direction of a basefilm as desired, and enables interconnection of films using a continuousroll-to-roll process.

[0003] (b) Description of the Related Art

[0004] The optical characteristics of a liquid crystal display panel arecontrolled by the application of a polarization film, a retardationfilm, and an optical compensation film. The optical compensation filmincludes a liquid crystal polymer having a predetermined orientation,and acts to adjust a color shift and a contrast ratio of the liquidcrystal panel to ensure a wide viewing angle. A conventional λ/4retardation film that varies a polarization pattern may be used for theoptical compensation film.

[0005] Such an optical compensation film is manufactured by performing arubbing treatment on a surface of the base film such that a valley of apredetermined direction is formed on the surface of the base film, afterwhich a liquid crystal material is deposited on the base film to orientliquid crystal molecules between the valleys.

[0006] In the conventional rubbing treatment, a rubbing cloth and thebase film are each respectively wound around a rubbing roller and a baseroller, and in a state where the rubbing cloth is in contact with thebase film, the rubbing roller is rotated in a direction opposite thedirection of movement of the base film. As a result, rubbing occursbetween the rubbing cloth and the base film. The rubbing direction istypically in the direction of movement of the base film.

[0007] However, there are instances when it becomes necessary to set alight transmission axis of the optical compensation film at apredetermined angle with a light transmission axis of the polarizationfilm or another optical compensation film. The light transmission axisof the optical compensation film is determined by the rubbing direction,while the light transmission axis of the polarization film is the sameas a stretching direction of the polarization film.

[0008] Accordingly, with reference to FIG. 1, a polarization film 1 istensed in a direction A such that the polarization film 1 ismanufactured having a light transmission axis in the direction A.Further, a rubbing treatment is performed on a base film 3 in thedirection A while it is also moved in the direction A, and a liquidcrystal material is deposited on the base film 3 to thereby produce alight compensation film 5. The light compensation film 5 is then cutdiagonally at a predetermined angle.

[0009] Subsequently, the polarization film 1 and the light compensationfilm 5 are combined into an integral unit while each has a lighttransmission axis of a predetermined angle. (Direction B in the drawingindicates the light transmission axis of the light compensation film 5.)

[0010] However, in the above method, since the films are individuallymanufactured in separate lines before being combined into a single unit,manufacture is complicated and overall production costs are increased.Further, there is waste in the above process in that the unused portionof the film that is cut is simply discarded.

[0011] Therefore, there is disclosed an off-axis rubbing process, inwhich the direction of movement and rubbing direction of the base filmare different such that a slanted light transmission axis in a desireddirection with respect to a lengthwise direction of the base film isobtained. Off-axis rubbing is typically performed by diagonally movingacross the base film with a rotating rubbing cloth.

[0012] Korean Laid-Open Patent No. 2000-12120 discloses a method relatedto the off-axis rubbing process. That is, a method is disclosed in whichsome of the base rollers are set to be off-axis such that some of thebase films are positioned diagonally with respect to rotating rubbingcloths. However, this and other conventional processes that useoff-center rubbing have many drawbacks.

[0013] In particular, the conventional off-center rubbing process cannotexceed a rubbing angle of 60°, and it is not possible to realize arubbing angle of 90° or greater. Because of this limitation in theapplicable rubbing angle, there are also limits in the variety of lighttransmission axes that can be obtained for the produced opticalcompensation films.

[0014] Further, with the diagonal positioning of some of the base films,it is possible to form an orientation surface on the base films in anunintended direction, or for friction to be generated such that creasesare formed in the base films. This negatively affects the quality andevenness of the liquid crystal material coated on the base films.

[0015] Finally, it is difficult to realize various rubbing angles and tofreely adjust the rubbing angle with the use of conventional off-axisrubbing. This rules out the possibility of performing a roll-to-rollprocess to combine the films of the optical compensation film, thepolarization film, and other optical compensation films. Hence,manufacture remains complicated and production costs remain high.

SUMMARY OF THE INVENTION

[0016] It is one object of the present invention to provide a rubbingdevice that allows for the realization of various rubbing angles andeasy adjustment of the rubbing angle such that optical compensationfilms may be manufactured that can be used in various types of liquidcrystal displays, and that enables interconnection of an opticalcompensation film, a polarization film, and other optical compensationfilms using a continuous roll-to-roll process to thereby simplify theoverall manufacturing process.

[0017] In one embodiment, the present invention provides a rubbingdevice including a base roller assembly that suspends and otherwisesupports a base film to convey the same in one direction; a rubbingroller assembly that suspends and otherwise supports a rubbing cloth,and that moves the rubbing cloth in a direction opposite a conveyingdirection of the base film to thereby realize a rubbing treatment bycontact between the rubbing cloth and the base film; and a rotatingapparatus provided under the rubbing roller assembly and that rotatesthe entire rubbing roller assembly to a particular angle within therange of 0˜180° in the or counterclockwise direction with respect to theconveying direction of the base film.

[0018] The base roller assembly includes first and second guide rollersthat support the base film and prevent slipping of the same, and a touchroller that contacts the base film to the rubbing cloth. Preferably, anadhesive is provided on an outer surface of the first and second guiderollers to prevent slipping of the base film.

[0019] The rubbing roller assembly includes a drive roller that isrotated by a motor, a tension guide roller that provides tension to therubbing cloth, and a guide roller that guides the rubbing cloth.Preferably, a crease-prevention plate is provided at a location betweenthe drive roller and the guide roller to prevent the generation ofcreases in the rubbing cloth.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate an embodiment of theinvention, and, together with the description, serve to explain theprinciples of the invention:

[0021]FIG. 1 is a schematic view of a conventional process to combine anoptical compensation film and a polarization film.

[0022]FIG. 2 is a side view of a rubbing device according to a preferredembodiment of the present invention.

[0023]FIG. 3 is a plan view of a base film and a base roller assembly ofFIG. 2.

[0024]FIG. 4 is a plan view of a rubbing cloth and a rubbing rollerassembly of FIG. 2.

[0025]FIGS. 5 and 6 are plan views showing a rubbing cloth and a rubbingroller assembly of FIG. 2 in a state of being rotated by a rotatingapparatus.

[0026]FIG. 7 is a schematic view of a process to combine an opticalcompensation film and a polarization film according to a preferredembodiment of the present invention.

[0027]FIG. 8 is a side view of a base roller assembly according toanother preferred embodiment of the present invention.

[0028]FIG. 9 is a plan view of a base roller assembly according toanother preferred embodiment of the present invention.

[0029]FIG. 10 is a schematic view used to describe a superposition angleof a base film.

[0030]FIG. 11 shows schematic views used to describe a rubbing angle andrubbing speed of an optical compensation film.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Preferred embodiments of the present invention will now bedescribed in detail with reference to the accompanying drawings.

[0032]FIG. 2 is a side view of a rubbing device according to a preferredembodiment of the present invention. A rubbing device 2 includes a baseroller assembly 6 that suspends and otherwise supports a base film 4 toconvey the same; a rubbing roller assembly 10 that suspends andotherwise supports a rubbing cloth 8, and that moves the rubbing cloth 8in a direction opposite a conveying direction of the base film 4; and arotating apparatus 12 that rotates the entire rubbing roller assembly 10to vary a rubbing angle.

[0033] The base roller assembly 6 includes first and second guiderollers 14 and 16 that support the base film 4 and prevent slipping ofthe same, and a touch roller 18 that contacts the base film 4 to therubbing cloth 8 and varies a rubbing depth and a rubbing length. Thebase film 4 is a polymer film such as polyethylene terephthalate (PET)or cellulose triacetate (TAC) that is flexible to allow for aroll-to-roll rubbing treatment.

[0034] With reference also to FIG. 3, the first guide roller 14, thesecond guide roller 16, and the touch roller 18 are arranged with theirrotational axes all in direction A such that the base film 4 is moved indirection B, which is perpendicular to direction A. The entire baseroller assembly 6 is driven by a winder (not shown), and a conveyingspeed and degree of tension in the base film 4 may be controlled by therotating speed of the winder.

[0035] The rubbing roller assembly 10 that supports the rubbing cloth 8includes a drive roller 20 that is rotated by a motor (not shown), atension guide roller 22 that provides tension to the rubbing cloth 8 toprevent the formation of creases in the rubbing cloth 8, and a guideroller 24 that acts to guide the rubbing cloth 8. The tension guideroller 22 can be moved up and down (in FIG. 2) to adjust the tension inthe rubbing cloth 8. Also, a crease prevention plate 26 is provided at alocation between the drive roller 20 and the guide roller 24, whichprevents the generation of creases in the rubbing cloth 8 that wouldreduce the effectiveness of the same.

[0036] Referring to FIG. 4, the drive roller 20, the guide roller 24,and the tension guide roller 22 are also arranged with their rotationalaxes in direction A such that the rubbing cloth 8 is conveyed alongdirection B. With the elements of the rubbing roller assembly 10 beingarranged in the same manner as the elements of the base roller assembly6, a rubbing angle, which is the angle between the conveying directionsof the base film 4 and the rubbing cloth 8, is 0°.

[0037] The entire rubbing roller assembly 10 is rotated by the rotatingapparatus 12, which is provided under the rubbing roller assembly 10, tothereby vary a rotating axis of the rubbing roller assembly 10. Therotating apparatus 12 includes a rotating plate 28 on which the rubbingroller assembly 10 is fixed, a drive motor 30 that rotates the rotatingplate 28, and a controller 32 that controls a degree of rotation (i.e.,a rotating angle) of the rotating plate 28.

[0038] With the operation of the rotating apparatus 12, with referenceto FIG. 5, the entire rubbing roller assembly 10 is rotated apredetermined angle in a counterclockwise direction (for example). As aresult, a rotating axis of the rubbing roller assembly 10 is changed todirection C so that the conveying direction of the rubbing cloth 8 is indirection D. A rubbing angle of θ is, therefore, formed betweendirection B of the base film 4 and direction D of the rubbing cloth 8.

[0039] In the preferred embodiment of the present invention, a rubbingangle of 90° is easily realized. The rotating apparatus 12 is able tochange the rubbing direction with respect to the base film 4 in a rangeof 0˜180° in both the clockwise and counterclockwise directions.

[0040] Therefore, in the preferred embodiment of the present invention,the conveying direction of the rubbing cloth 8 is easily changed byoperation of the rotating apparatus 12 and without requiringre-positioning of the base film 4, and an optical compensation filmhaving various light transmission axes may be easily produced. Further,the interconnection of the optical compensation film, the polarizationfilm, and other optical compensation films may be formed in aroll-to-roll process to thereby simplify production.

[0041] In particular, with reference to FIG. 7, a rubbing treatment isperformed using the rubbing device 2 in direction D with respect to theconveying direction (direction B) of the base film 4. Subsequently, aliquid crystal material is deposited on the base film 4 to therebyproduce an optical compensation film. Next, a polarization film 34,which is tensed in direction A, is adhered to the optical compensationfilm and the films are combined through a continuous roll-to-rollprocess.

[0042] Therefore, an optical compensation film, a polarization film, andother optical compensation films may be combined in a continuousprocess, and the resulting film is cut to obtain the final product. Withthis capability, the film utilization efficiency is improved, andproduction is made easy to reduce overall manufacturing costs. Further,since the rubbing angle is easily varied by operating the rotatingapparatus 12, optical compensation films having various lighttransmission axes may be easily produced in a continuous roll-to-rollprocess.

[0043] In the case where the rubbing direction is different from thedirection that the base film 4 is conveyed, it is possible for the basefilm 4 to slip or for creases to form on the base film 4 as a result offriction that is produced between the base film 4 and the rubbing cloth8. Therefore, with reference to FIG. 8, an adhesive 36 such as siliconrubber is applied to an outer surface of the first and second guiderollers 14 and 16 to thereby prevent the problem of slipping of the basefilm 4 or the formation of creases thereon.

[0044] Further, with reference to FIG. 9, the positions of the firstguide roller 14, the second guide roller 16, and the touch roller 18 arechanged to adjust a superposition angle of the base film 4. As a result,rubbing length, rubbing depth, rubbing density, etc. are easilycontrolled. As shown in FIG. 10, the superposition angle (Ψ) is definedby the angle between two lines drawn from a center (◯) of the touchroller 18 to two points C1 and C2 where the base film 4 initially makescontact with the touch roller 18.

[0045] In more detail, the first and second guide rollers 14 and 16 aremoveably provided so that they may be positioned closer together orfarther apart (i.e., so that they can be moved in a horizontal directionin FIG. 2), and the touch roller 18 is provided so that its position maybe varied with respect to the rubbing cloth (i.e., so that it may bemoved vertically in FIG. 2).

[0046] With such varying of the positions of the rollers 14, 16, and 18,the superposition angle (Ψ) may be varied in the range of 0˜270°. Therubbing length, rubbing depth, rubbing density, etc. may be adjusted byvarying the superposition angle (Ψ).

[0047] In FIG. 11, Vs indicates a conveying speed of the base film, andRaxis indicates a rotating axis of the rubbing cloth 8 that is slantedby as much as the rubbing angle θ with respect to a conveying directionof the base film 4. Further, the rubbing speed Vs is divided into acomponent R_(P) that is parallel to the conveying direction of the basefilm 4, and a component R_(N) that is normal to the conveying directionof the base film 4.

[0048] Since the rubbing cloth 8 is rotated in a direction opposite theconveying direction of the base film 4, a rubbing speed Ro that isparallel with the actual conveying direction of the base film 4 iscalculated by the following equation.

R _(O) =R _(P) −V _(S)   [Equation 1]

[0049] Accordingly, a total rubbing speed V_(T) and an effective rubbingangle Θ eff are as shown respectively in Equations 2 and 3 below.

V _(T)={square root}{square root over (R _(O) ² +R _(N) ²)}  [Equation2]

[0050] [Equation 3]$\Theta_{eff} = {\arcsin \left( \frac{R_{N}}{V_{T}} \right)}$

[0051] The rubbing length is proportional to the superposition angle(Ψ), a diameter of the touch roller 18, and rubbing speed, and it isinversely proportional to the conveying speed of the base film 4.Accordingly, a contact time (t) and a rubbing length (lt) of the basefilm 4 and the rubbing cloth 8 are respectively as shown in Equation 4and Equation 5 below.

[0052] [Equation 4]$t = \frac{\left( {\pi \quad d\quad {\Psi/360}} \right)}{V_{S}}$

l _(t) =V _(T) xt   [Equation 5]

[0053] In the preferred embodiment of the present invention, in order toorient liquid crystal material on the base film 4 in the best possibledirection, the various variables in the above equations are manipulated,and the most effective rubbing angle, rubbing depth, etc. are easilyobtained.

[0054] With the use of the rubbing device of the present invention, therubbing angle may be easily varied in the range of 0˜180° in both theclockwise and counterclockwise directions such that an opticalcompensation film that can be used in various types of LCDs may beproduced. Further, the interconnection of the optical compensation film,the polarization film, and other optical compensation films may beformed in a roll-to-roll process to thereby simplify production.

[0055] Although preferred embodiments of the present invention have beendescribed in detail hereinabove, it should be clearly understood thatmany variations and/or modifications of the basic inventive conceptsherein taught which may appear to those skilled in the present art willstill fall within the spirit and scope of the present invention, asdefined in the appended claims.

What is claimed is:
 1. A rubbing device, comprising: a base rollerassembly that suspends and otherwise supports a base film to convey thesame in one direction; a rubbing roller assembly that suspends andotherwise supports a rubbing cloth, and that moves the rubbing cloth ina direction opposite a conveying direction of the base film to therebyrealize a rubbing treatment by contact between the rubbing cloth and thebase film; and a rotating apparatus provided under the rubbing rollerassembly and that rotates the entire rubbing roller assembly to aparticular angle within the range of 0˜180° in the clockwise orcounterclockwise direction with respect to the conveying direction ofthe base film.
 2. The rubbing device of claim 1, wherein the base rollerassembly includes first and second guide rollers that support the basefilm and prevent slipping of the same, and a touch roller that contactsthe base film to the rubbing cloth.
 3. The rubbing device of claim 1,wherein the base film is polyethylene terephthalate (PET) or cellulosetriacetate (TAC).
 4. The rubbing device of claim 2, wherein the firstguide roller, the second guide roller, and the touch roller are arrangedwith rotational axes thereof all in an identical direction such that thebase film is conveyed in a direction perpendicular to the direction ofthe rotational axes of the first guide roller, the second guide roller,and the touch roller.
 5. The rubbing device of claim 2, furthercomprising an adhesive that is provided on outer surfaces of the firstand second guide rollers to prevent slipping of the base film.
 6. Therubbing device of claim 5, wherein the adhesive is silicon rubber. 7.The rubbing device of claim 2, wherein the first guide roller, thesecond guide roller, and the touch roller are able to be re-positionedin a horizontal or vertical direction to adjust superposition angle ofthe base film.
 8. The rubbing device of claim 7, wherein the first andsecond guide rollers are moved in a horizontal direction to haverelative positions closer together or farther apart.
 9. The rubbingdevice of claim 7, wherein the touch roller is moved in up and downdirections to be positioned closer to or farther from the rubbing cloth.10. The rubbing device of claim 1, wherein the rubbing roller assemblyincludes a drive roller that is rotated by a motor, a tension guideroller that provides tension to the rubbing cloth, and a guide rollerthat guides the rubbing cloth.
 11. The rubbing device of claim 10,wherein the tension guide roller is moved up and down to adjust atension in the rubbing cloth.
 12. The rubbing device of claim 10,further comprising a crease prevention plate provided at a locationbetween the drive roller and the guide roller, the crease preventionplate preventing the generation of creases in the rubbing cloth.
 13. Therubbing device of claim 10, wherein the drive roller, tension guideroller, and guide roller are arranged with rotational axes in anidentical direction such that the rubbing cloth is conveyed in adirection perpendicular to the direction of the rotational axes of thedrive roller, tension guide roller, and guide roller.
 14. The rubbingdevice of claim 1, wherein the rotating apparatus includes a rotatingplate on which the rubbing roller assembly is fixed, a drive motor thatrotates the rotating plate, and a controller that controls a rotatingangle of the rotating plate.